The present invention relates to a photosensitive composition and a powder pattern forming process using such a composition.
The formation of powder layer pattern is carried out in, for example, preparation of a color picture tube. The interior side of the face plate of a color picture tube is coated with three different kinds of phosphors in dots or in stripes and among these phosphors, black powder is applied to form black matrix. Up to this time, a color picture tube has generally been produced as follows: First, black matrix is formed in the interior side of the face plate. A mixed coating material composed of a phosphor for the first color and a photosensitive composition is applied on the black matrix, dried, patternwise exposed to light to insolubilize the photosensitive composition at the exposed portion and washed with water, thus retaining an insolubilized portion alone on the face plate while removing the other portion. For phosphors for the second and third colors, a similar procedure is repeated respectively. Though a method of forming black matrix will not be described in detail here, it is more complicated than that of phosphor pattern. As described above, the color picture tube phosphor surface forming process is complicated and multiple runs of wet coating, water washing and drying are required.
As an improvement in such a process, some of the inventors of the present invention have previously proposed, in Japanese Laid-Open patent application No. 126861/78 (U.S. Pat. No. 4,273,842), a method of forming a color picture tube phosphor surface in a simple manner. This method was attained on the basis of a new finding that the photolytic product of an aromatic diazonium salt is able to accept powder particles, and it comprises (1) coating the inner surface of the face plate of a color picture tube with a photosensitive composition containing an aromatic diazonium salt as a photosensitive component and getting sticky by light exposure, thereby forming a coating layer on said surface, (2) subjecting said coating layer to patternwise exposure to make the exposed portion sticky and (3) contacting powder particles with the exposed portion to have said powder particles accepted by said coating layer. According to this method, the rest of powder particles can be easily removed by air spray or the like. Therefore, mere repetition of exposure and powder contact is required for the phosphors of the second and third colors and, if necessary, black matrix can also be formed according to the method. Further, once the coating layer is formed, it is possible to form as many phosphor powder patterns as desired.
Though the above method has advantages of saving of water and simplification of the forming step, it has also a problem in that the photosensitive composition has a somewhat lower sensitivity than that of the prior art.